Abstract
The centrality dependence of pseudorapidity density of charged particles (dN(ch)/d eta) in Cu + Cu (Au + Au) collisions at Relativistic Heavy Ion Collider energy of root S-NN = 22.4 , 62.4 and 200 (19.6, 62.4 and 200) GeV, is investigated within an improved HIJING code. The standard HIJING model is enhanced by a prescription for collective nucleon-nucleon (NN) interactions and more modern parton distribution functions. The collective NN-interactions are used to induce both cascade and nucleon shadowing effects. We find collective cascade broadens the pseudorapidity distributions in the tails (at vertical bar eta vertical bar > y(beam)) above 25%-30% collision centrality to be consistent with the dN(ch)/d eta at root S-NN 19.6, 62.4 GeV. The overall contribution of nucleon shadowing is shown to depress the whole shape of dN(ch)/d eta in the primary interaction region (at vertical bar eta vertical bar > y(beam)) for semiperipheral (20%-25%) and peripheral (>= 35%-40%) Cu + Cu (Au + Au) interactions at root S-NN = 200 GeV, in accordance with the PHOBOS data.